Sheet conveyance device and image forming apparatus

Abstract

To provide a sheet carrier and image forming apparatus capable of improving the performance of skew correction.SOLUTION: A sheet carrier comprises a carrier roller pair 47 that transports a sheet, a register roller pair 23 for transporting a sheet S that has a nip N3 against which a front end S1 of the sheet S transported by the carrier roller pair 47 abuts to allow forming of a loop in the sheet S, a curved outer guide 60 that guides the sheet S transported by the carrier roller pair 47 to the register roller pair 23, and a roll 64 that is arranged along the outer guide 60 and to be rotated with respect to a slide surface, on the outer guide 60, of the sheet S being guided by the outer guide 60.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a sheet conveying device for conveying a sheet and an image forming apparatus including the same.

Background Art

[0002] Generally, an image forming apparatus is known that guides a sheet having an image formed on a first surface back to an image forming unit via a reverse conveyance path and a duplex conveyance path, and forms an image on a second surface of the sheet in the image forming unit. Conventionally, an image forming apparatus has been proposed that guides a sheet from a duplex conveyance path to a pair of loop rollers on a main conveyance path, and abuts the sheet against a pair of registration rollers in a stopped state by the pair of loop rollers to correct skewing of the sheet (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The image forming apparatus described in Patent Document 1 is configured to be curved in the vicinity of the confluence portion with the main conveyance path of the duplex conveyance path, aiming to reduce the size of the image forming apparatus. However, when the sheet passes through such a curved conveyance path, the sheet is pressed against a curved guide constituting the curved conveyance path, and the frictional resistance between the sheet and the curved guide increases.

[0005] For example, in the image forming apparatus described in Patent Document 1, when the loop roller pair further conveys the sheet in a state where the leading edge of the sheet abuts against the registration roller pair, a loop is formed in the sheet. At this time, since the sheet is pressed against the curved guide, the frictional resistance between the sheet and the curved guide increases, and it becomes difficult to transmit the conveying force of the sheet by the loop roller pair to the leading edge of the sheet. As a result, the force with which the leading edge of the sheet is pressed against the nip of the registration roller pair is reduced, and there is a problem that the skew correction performance deteriorates.

[0006] Therefore, an object of the present invention is 、Upper to provide a sheet conveying device that solves the above-described problems and an image forming apparatus including the same.

Means for Solving the Problems

[0007] The present invention provides a sheet conveying device including: a first conveying unit including a first roller that conveys a sheet and a second roller that rotates about the same rotation axis as the first roller and conveys the sheet; a second conveying unit having an abutting portion that can form a bend in the sheet when the leading edge of the sheet conveyed by the first conveying unit abuts thereon and conveys the sheet; a first guide that guides the sheet conveyed by the first conveying unit to the second conveying unit; and a second guide that is opposed to the first guide and guides the sheet conveyed by the first conveying unit to the second conveying unit, the second guide forming a conveying path including a curved curved region between the first conveying unit and the second conveying unit together with the first guide 、Front a first rotating body disposed in the curved region and configured not to nip the sheet conveyed by the first roller and the second roller 、Front a second rotating body disposed in the curved region and configured not to nip the sheet conveyed by the first roller and the second roller 、FrontA third rotating body disposed in the curved region and configured not to nip the sheet conveyed by the first roller and the second roller, and the conveyance path and the first guide are disposed outside the second guide in the bending direction in the curved region, and the first rotating body, the second rotating body, and the third rotating body are disposed outside the second guide in the bending direction in the curved region so as to be in contact with the surface of the sheet guided by the first guide and rotate passively. The first roller is disposed on one side of the second roller in the width direction orthogonal to the sheet conveyance direction, the first rotating body is disposed on the one side of the first roller in the width direction, and the second rotating body is disposed on the other side opposite to the one side of the second roller in the width direction. The third rotating body is disposed between the first roller and the second roller in the width direction, and the first rotating body, the second rotating body, and the third rotating body are disposed so as to overlap each other when viewed in the width direction. The first roller and the second roller correct the skew of the sheet by conveying the sheet in a state where the leading end of the sheet abuts against the abutting portion, and the first rotating body, the second rotating body, and the third rotating body rotate passively with respect to the sheet when the leading end of the sheet abuts against the abutting portion and the skew of the sheet is corrected. This is the gist of the invention.

Effect of the Invention

[0008] According to the present invention 、Diagonal The line correction ability can be improved.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0010] <The First Embodiment> 〔Overall Configuration〕 First, the first embodiment of the present invention will be described. The printer 100 as an image forming apparatus is an electrophotographic full-color laser beam printer. As shown in FIG. 1, the printer 100 has a printer main body 115 and a reading device 120 installed on the upper part of the printer main body 115.

[0011] The printer main body 115 includes an image forming unit 71 that forms an image on a sheet S, a feeding unit 72, a fixing unit 3, a discharging and reversing unit 73, and a duplex conveying unit 74. The image forming unit 71 includes four drum units 11Y, 11M, 11C, 11K, four developing units 10Y, 10M, 10C, 10K, toner storage units TY, TM, TC, TK, and a scanner unit 12. Each drum unit and each developing unit are detachably provided with respect to the printer main body 115. The four drum units 11Y, 11M, 11C, 11K and the four developing units 10Y, 10M, 10C, 10K have the same configuration except that the colors of the images to be formed are different. Therefore, only the configuration of the drum unit 11Y and the developing unit 10Y and the image forming process will be described, and the description of the other drum units and developing units will be omitted.

[0012] The drum unit 11Y includes a photosensitive drum 110, a charging means (not shown), and a cleaning means (not shown). The photosensitive drum 110 is configured by applying an organic photoconductive layer on the outer periphery of an aluminum cylinder and rotates by a drive motor (not shown). The cleaning means cleans the toner that has not been completely transferred from the photosensitive drum 110.

[0013] In addition, the image forming unit 71 is provided with an intermediate transfer belt 13 wound around a drive roller 13a, a secondary transfer opposing roller 13b, etc. Inside the intermediate transfer belt 13, primary transfer rollers 14Y, 14M, 14C, 14K are provided. Further, a secondary transfer roller 24 is provided opposite to the secondary transfer opposing roller 13b so as to sandwich the intermediate transfer belt 13. The intermediate transfer belt 13 and the secondary transfer roller 24 form a transfer nip N1 as an image forming portion that transfers an image to the conveyed sheet S.

[0014] The feeding unit 72 is provided at the lower part of the printer main body 115 and includes a cassette 21 that supports the sheet S and a pickup roller 17 that feeds the sheet S supported by the cassette 21. Further, the feeding unit 72 includes a separating roller pair 18 that separates the sheets S fed by the pickup roller 17 one by one. The fixing unit 3 has a fixing roller 3a and a pressure roller 3b that are formed in a hollow shape, and a heater (not shown) and a temperature sensor that measures the temperature of the heater are built into the fixing roller 3a.

[0015] Here, each conveyance path provided in the printer main body 115 and the components for conveying the sheet will be described. The printer main body 115 has a feeding conveyance path R1, a discharge conveyance path R2 and a reverse conveyance path R3 that branch off at a branch point BP1 which is the downstream end of the sheet conveyance direction of the feeding conveyance path R1, and a duplex conveyance path R4 where the reverse conveyance path R3 merges at a merging point BP2. The duplex conveyance path R4 guides the sheet with an image formed on the first side by the transfer nip N1 back toward the transfer nip N1 and merges with the feeding conveyance path R1 at the merging point BP3.

[0016] A discharge roller pair 42 for discharging the sheet S to the discharge tray 5 is provided in the discharge conveyance path R2, and a reverse roller pair 44 that is configured to be reversible in forward and reverse directions and can switch back the sheet S for reverse conveyance is provided in the duplex conveyance path R4. Further, a conveyance roller pair 43 is provided in the reverse conveyance path R3, and conveyance roller pairs 45, 46, 47 are provided in the duplex conveyance path R4. Near the merging point BP3 of the feeding conveyance path R1, a registration roller pair (hereinafter referred to as a registration roller pair) 23 is provided.

[0017] Next, the image forming operation of the printer 100 configured as described above will be explained. When image data read by a personal computer or a reading device 120 (not shown) is input to the scanner unit 12, laser light corresponding to the image data is irradiated from the scanner unit 12 onto the photosensitive drum 110 of the drum unit 11Y. Note that the image data read by the reading device 120 is sent to the control device 6 and stored.

[0018] At this time, the surface of the photosensitive drum 110 is uniformly charged to a predetermined polarity and potential in advance by the charging roller, and an electrostatic latent image is formed on the surface by irradiating laser light from the scanner unit 12. The electrostatic latent image formed on the photosensitive drum 110 is developed by the developing unit 10Y supplied with toner from the toner storage unit TY, and a yellow (Y) toner image is formed on the photosensitive drum 110.

[0019] Similarly, after the photosensitive drums of the drum units 11M, 11C, and 11K are irradiated with laser light from the scanner unit 12, magenta (M), cyan (C), and black (K) toner images are formed by the developing units 10M, 10C, and 10K. The toner images of each color formed on each photosensitive drum are transferred to the intermediate transfer belt 13 by the primary transfer rollers 14Y, 14M, 14C, and 14K, and are conveyed to the transfer nip N1 by the intermediate transfer belt 13 rotated by the drive roller 13a. Note that each color image forming process is performed at a timing to overlap with the upstream toner image primarily transferred onto the intermediate transfer belt 13. Also, the toner remaining on the photosensitive drum 110 after the transfer of the toner image is recovered by the cleaning blade.

[0020] In parallel with this image forming process, the sheet S housed in the cassette 21 of the feeding unit 72 is sent out by the pickup roller 17 and separated one by one by the separation roller pair 18. Then, the skew of the sheet S is corrected by the registration roller pair 23, and the sheet S is conveyed at a predetermined conveyance timing in accordance with the transfer timing of the image at the transfer nip N1.

[0021] Then, on the sheet S, a full-color toner image on the intermediate transfer belt 13 is transferred at the transfer nip N1 by the secondary transfer bias applied to the secondary transfer roller 24. The sheet S onto which the toner image has been transferred is given predetermined heat and pressure by the fixing roller 3a and the pressure roller 3b of the fixing unit 3, and the toner is melted and fixed (fixed). The sheet S that has passed through the fixing unit 3 is conveyed to the discharge conveyance path R2 by the conveyance roller pair 41 and discharged to the discharge tray 5 by the discharge roller pair 42.

[0022] When a duplex printing job for forming images on both sides of the sheet is input, the sheet S on which the image has been formed on the first side and has passed through the fixing unit 3 is guided to the reverse conveyance path R3 by a guiding member (not shown). When the sheet is conveyed to the reverse roller pair 44 by the conveyance roller pair 43, the reverse roller pair 44 first conveys the sheet S in the direction of discharging it outside the machine. Then, when the trailing edge of the sheet S passes through the confluence point BP2, the reverse roller pair 44 reverses, and the sheet S reversed by the reverse roller pair 44 is conveyed through the duplex conveyance path R4.

[0023] The sheet S is conveyed by the conveyance roller pairs 45, 46, 47 and merges into the feeding conveyance path R1 at the confluence point BP3. The sheet S that has merged into the feeding conveyance path R1 has its skew corrected by the registration roller pair 23, and then an image is formed on the second side in the same manner as on the first side and is discharged to the discharge tray 5.

[0024] [Skew correction operation during duplex printing] Next, the skew correction operation on the sheet when the printer 100 executes a duplex printing job will be described. First, the configuration around the duplex conveyance path R4 and the registration roller pair 23 will be described. As shown in FIG. 2, the duplex conveyance path R4 has a curved conveyance path R5 between the first conveyance unit and the conveyance roller pair 47 as the first roller pair, and the second conveyance unit and the registration roller pair 23 as the second roller pair. That is, the curved conveyance path R5 constitutes a part of the duplex conveyance path R4.

[0025] The curved conveyance path R5 is formed by an outer guide 60 as a curved guide portion, an inner guide 61 facing the outer guide 60, and a pre-registration guide 66. The outer guide 60 is disposed outside the inner guide 61 in the bending direction of the curved conveyance path R5. That is, at least a part of the curved conveyance path R5 is formed by the outer guide 60 and the inner guide 61.

[0026] Near the confluence point BP3 of the curved conveyance path R5, a loop space 65 is formed and a confluence sheet 63 made of a sheet member is provided. Further, a roller 64 is provided along the outer guide 60. When viewed in the axial direction of the roller 64, a part of the roller 64 overlaps the curved conveyance path R5. The roller 64 does not sandwich the sheet together with other rotating bodies. The conveyance roller pair 47, the registration roller pair 23, the outer guide 60, and the roller 64 constitute a sheet conveyance device 200 that conveys the sheet S.

[0027] Let the conveyance direction of the sheet by the conveyance roller pair 47, that is, the conveyance direction of the sheet at the nip N2 of the conveyance roller pair 47 be the conveyance direction D1, and the conveyance direction of the sheet by the registration roller pair 23, that is, the conveyance direction of the sheet at the nip N3 of the registration roller pair 23 be the conveyance direction D2. In the present embodiment, the relative angle D between the conveyance direction D1 and the conveyance direction D2 is set to 167°. That is, the conveyance direction D1 and the conveyance direction D2 are substantially opposite directions, and the sheet S conveyed in the conveyance direction D1 by the conveyance roller pair 47 is guided by the curved conveyance path R5 so as to be in a substantially opposite direction.

[0028] Next, the skew correction operation during double-sided printing and the state of the sheet S at that time will be described with reference to FIGS. 3 to 7. FIG. 3 is a diagram showing a state when the sheet S is fed into the curved conveyance path R5. As shown in FIG. 3, the sheet S is sent to the curved conveyance path R5 by the conveyance roller pairs 45, 46, 47 (see FIG. 1). While the leading end S1 slides on the outer guide 60, the middle portion S2 slides on the inner guide 61 as an opposing guide portion. Then, the sheet S is guided toward the registration roller pair 23 while the conveyance direction is changed by the outer guide 60 and the inner guide 61.

[0029] At this time, the sheet S is supported at three points by the outer guide 60, the inner guide 61, and the pair of conveying rollers 47. In the vicinity downstream of the pair of conveying rollers 47 in the sheet conveying direction, due to the rigidity of the sheet S itself, a space A is likely to be formed between the sheet S and the outer guide 60.

[0030] FIG. 4 is a view showing a state immediately after the leading end S1 of the sheet S abuts against the registration roller pair 23. As shown in FIG. 4, after the leading end S1 of the sheet S is guided by the outer guide 60, it is guided to the registration roller pair 23 by the joining sheet 63. Then, the leading end S1 of the sheet S abuts against the nip N3 of the stopped registration roller pair 23. The nip N3 can form a loop in the sheet S when the leading end S1 of the sheet S abuts. The sheet S immediately after abutting against the nip N3 as the abutting portion is curved through the curved conveying path R5 having a curved shape and is curved into a U-shaped shape having a substantially arc shape. At this time, the vicinity of the leading end S1 of the sheet S is supported by the rigidity of the sheet S itself, and a space B is likely to be formed between the pre-registration guide 66 and the sheet S.

[0031] Also, the vicinity of the pair of conveying rollers 47 is supported by the rigidity of the sheet S itself and the pair of conveying rollers 47, and the space A between the sheet S and the outer guide 60 is likely to be maintained. Therefore, the vicinity of the apex RT of the U-shaped curved conveying path R5 sandwiched between the space A and the space B becomes the portion most likely to be in strong contact with the sheet S. Therefore, in the present embodiment, a roller 64 is provided in the vicinity of the apex RT of the curved conveying path R5, and the roller 64 reduces the frictional resistance between the sheet S and the outer guide 60. The roller 64 as a rotating body can rotate passively with respect to the surface sliding on the outer guide 60.

[0032] FIG. 5 is a diagram showing the state immediately after the sheet S starts to form a loop. When the conveying roller pair 47 conveys the sheet S in a state where the leading end S1 abuts against the nip N3 of the registration roller pair 23, the sheet S comes into contact with the outer guide 60 from the apex of the U-shaped bend of the sheet S toward the conveying roller pair 47. As a result, the space A near the downstream of the conveying roller pair 47 in the sheet conveying direction is filled. This is because there is frictional resistance between the sheet S and the outer guide 60 near the apex RT of the curved conveying path R5, making it difficult for the apex portion of the bend of the sheet S to move. For this reason, the conveying force of the conveying roller pair 47 is transmitted to the sheet S in front of the apex RT of the curved conveying path R5, and a loop is formed in the sheet S so that the space A is filled.

[0033] FIG. 6 is a diagram showing the state immediately after a predetermined loop necessary for skew correction of the sheet S is formed in the loop space 65. When the sheet S in the state of abutting against the nip N3 is further conveyed by the conveying roller pair 47 from the state of FIG. 5, the sheet S forms a loop in the loop space 65. At this time, the sheet S contacts the pre-registration guide 66, and the space B is filled. At this time, the frictional resistance at the contact surface between the sheet S and the outer guide 60 is likely to be maximized. The portion of the outer guide 60 where the frictional resistance is maximized is the contact portion with the sheet S between near the apex RT and the conveying roller pair 47. In the present embodiment, the roller 64 is arranged at this portion to reduce the frictional resistance between the sheet S and the outer guide 60.

[0034] Here, the conveying force of the conveying roller pair 47 is used as a force to convey the sheet S against this frictional resistance, and a force to abut the leading end S1 of the sheet S against the nip N3 of the registration roller pair 23, form a loop in the sheet S, and correct the skew. That is, the smaller the frictional resistance between the sheet S and the outer guide 60, the easier it is for the conveying force of the conveying roller pair 47 to be transmitted to the leading end S1 of the sheet S. And by reducing the frictional resistance between the sheet S and the outer guide 60 by the roller 64, the leading end S1 of the sheet S is surely pressed against the nip N3 and is likely to be aligned following the nip N3, and the skew correction ability can be improved.

[0035] FIG. 7 is a diagram showing a state in which the registration roller pair 23 is transporting the sheet S after skew correction of the sheet S. When the skew of the sheet S is corrected by the registration roller pair 23, the registration roller pair 23 starts rotating, and the sheet S is transported toward the transfer nip N1 (see FIG. 1). In order for the registration roller pair 23 to stably transport the sheet S, it is necessary to prevent the sheet S from being pulled between the registration roller pair 23 and the transport roller pair 47. That is, even after the skew correction of the sheet S, it is desirable to transport the sheet S while maintaining a certain amount of loop.

[0036] The roller 64 rotates in a driven manner with respect to the sheet S even after the skew correction of the sheet S, and reduces the frictional resistance between the sheet S and the outer guide 60. Thereby, the conveying force of the conveying roller pair 47 can be efficiently transmitted to the leading end side of the sheet S, and it can be reduced that the sheet S is pulled between the registration roller pair 23 and the conveying roller pair 47. And since the sheet S is stably conveyed, for example, the formation of wrinkles in the sheet S can be reduced, and the image can be accurately transferred to the sheet S at the transfer nip N1 (see FIG. 1).

[0037] [Roller] Next, the configuration and arrangement of the roller 64 will be described in detail. As shown in FIG. 8, a plurality of rollers 64 are arranged in parallel in the width direction orthogonal to the sheet conveying direction (four in the present embodiment). Hereinafter, the four rollers will be referred to as rollers 64a, 64b, 64c, and 64d, respectively. Since the inertia of the roller 64 itself becomes a resistance to the sheet S, it is easier to reduce the frictional resistance when the inertia of the roller 64 itself is small. For this reason, in the present embodiment, four small rollers 64a, 64b, 64c, and 64d are provided to further reduce the frictional resistance. The transport roller pair 47 includes two rollers 47a and 47b arranged in parallel in the width direction, and a shaft portion 47c that rotatably supports these rollers 47a and 47b.

[0038] FIG. 9 is a schematic diagram showing the arrangement of the rollers 47a and 47b of the conveying roller pair 47 and the rollers 64a, 64b, 64c, and 64d. For example, when there is a curl or the like at the corner of the sheet S, the conveyed sheet S may be caught by the rollers 64a, 64b, 64c, and 64d. For this reason, in the present embodiment, the four rollers 64a, 64b, 64c, and 64d are arranged so as to be within the sheet width H1 in the width direction of the smallest size sheet that the printer 100 can convey. That is, the distance H2 between the outer surfaces of the roller 64a and the roller 64d in the width direction is equal to or less than the sheet width H1, and the rollers 64a, 64b, 64c, and 64d are provided symmetrically with respect to the center in the width direction of the curved conveyance path R5.

[0039] Furthermore, between the rollers 47a and 47b of the conveying roller pair 47 in the width direction, a stronger conveying force acts on the sheet S than at other locations. For this reason, it is desirable that at least one roller be provided within the region H3 between the outer surfaces of the roller 47a and the roller 47b of the conveying roller pair 47 in the width direction. In the present embodiment, two rollers 64b and 64c are provided within the region H3.

[0040] FIG. 10 is a diagram for explaining the arrangement of the rollers 64 in the sheet conveying direction. Since the frictional resistance between the sheet S and the outer guide 60 increases as the curvature of the curved conveyance path R5 increases, the roller 64 is more effective as the relative angle D (see FIG. 2) between the conveying direction D1 and the conveying direction D2 approaches 180°. In particular, it is effective when the relative angle D forms an angle of 120° or more. In the present embodiment, when the relative angle D between the conveying direction D1 and the conveying direction D2 is 120° or more and 240° or less, it is assumed that the conveying direction D1 and the conveying direction D2 are substantially opposite directions.

[0041] In addition, as shown in FIG. 10, the roller 64 is disposed along the conveyance section 53 that extends from the upstream end R5a of the curved conveyance path R5 to three-fifths of the entire length section L1 from the upstream end R5a to the downstream end R5b of the curved conveyance path R5 in the sheet conveyance direction. This is because the frictional resistance between the sheet S and the outer guide 60 tends to increase in this conveyance section 53. More specifically, it is preferable that the roller 64 is disposed along the conveyance section between the apex RT located at the center in the sheet conveyance direction of the entire length section L1 and the upstream end R5a of the curved conveyance path R5.

[0042] As described above, in the present embodiment, the roller 64 that rotates in a driven manner with respect to the sheet S is disposed at a position where the frictional resistance between the curved conveyance path R5 and the sheet S and the outer guide 60 increases, and the frictional resistance can be reduced. As a result, the leading end S1 of the sheet S is surely pressed against the nip N3 and is easily aligned following the nip N3, and the skew correction ability can be improved. Further, after the skew correction of the sheet S, the sheet S is stably conveyed, so that, for example, the formation of wrinkles in the sheet S can be reduced, and the image can be accurately transferred to the sheet S at the transfer nip N1.

[0043] <Second Embodiment> Next, a second embodiment of the present invention will be described. The second embodiment is configured such that the outer guide 60 and the inner guide 61 of the first embodiment are composed of a plurality of guide members. Therefore, for the same configuration as that of the first embodiment, illustration is omitted or the same reference numerals are given in the drawings for explanation.

[0044] As shown in FIG. 11, the curved conveyance path R5 is formed by an outer guide 160 as a curved guide portion, an inner guide 161 as an opposing guide portion, and a pre-feed guide 66. The outer guide 160 has outer guide members 60a and 60b, and the inner guide 161 has inner guide members 61a and 61b. Thus, even if the outer guide 160 and the inner guide 161 are constituted by a plurality of guide members, as long as the sheet S is guided so as to curve when the leading end S1 of the sheet S abuts against the nip N3, the roller 64 exhibits the same effect as in the first embodiment.

[0045] <Third Embodiment> Next, a third embodiment of the present invention will be described. The third embodiment is configured by arranging conveyance roller pairs 47 and registration roller pairs 23 other than the upstream end R5a and the downstream end R5b in the sheet conveyance direction of the curved conveyance path R5. Therefore, for the same configurations as in the first embodiment, illustration is omitted or the same reference numerals are given in the drawings for explanation.

[0046] In the present embodiment, as shown in FIG. 12, the conveyance roller pair 47 is arranged upstream by a distance L0 in the sheet conveyance direction from the upstream end R5a of the curved conveyance path R5, and the registration roller pair 23 is arranged downstream by a distance L2 in the sheet conveyance direction from the downstream end R5b. That is, it is not limited to the form in which the conveyance roller pair 47 and the registration roller pair 23 are arranged at the upstream end and the downstream end of the curved conveyance path R5 as in the first embodiment.

[0047] Also in the case of the present embodiment, it is preferable that the roller 64 is arranged at a position along the conveyance section 53 up to three-fifths of the entire length section L1 from the upstream end R5a to the downstream end R5b of the curved conveyance path R5 in the sheet conveyance direction. More specifically, it is preferable that the roller 64 is arranged at a position along the conveyance section between the apex RT located at the center in the sheet conveyance direction of the entire length section L1 and the upstream end R5a of the curved conveyance path R5.

[0048] In addition, in the present embodiment, the case where the roller 64 is disposed in a part of the curved conveyance path R5 in the double-sided conveyance path R4 has been described as an example, but the present invention is not limited thereto. For example, not limited to the double-sided conveyance path R4 through which the sheet S passes during double-sided printing, in other conveyance paths such as the feeding conveyance path R1, the discharging conveyance path R2, and the reversing conveyance path R3, if it is a conveyance path for bending the sheet S, the roller 64 may be disposed.

[0049] Further, in any of the above-described embodiments, the leading end S1 of the sheet S is abutted against the nip N3 of the registration roller pair 23 to correct skew, but the present invention is not limited thereto. For example, a shutter member as an abutting portion may be provided upstream of the nip N3 in the sheet conveyance direction, and the leading end S1 of the sheet S may be abutted against the shutter member to correct skew. Further, in any of the above-described embodiments, the inner guides 61 and 161 are provided to face the outer guides 60 and 160, but the inner guides 61 and 161 may be omitted.

[0050] Further, in any of the above-described embodiments, the electrophotographic printer 100 has been described, but the present invention is not limited thereto. For example, the present invention can also be applied to an inkjet image forming apparatus that forms an image on a sheet by discharging an ink liquid from a nozzle.

Explanation of Reference Numerals

[0051] 23: Second conveyance unit, second roller pair (registration roller pair) / 47: First conveyance unit, first roller pair (conveyance roller pair) / 53: Conveyance section / 60, 160: Curved guide section (outer guide) / 61, 161: Opposing guide section (inner guide) / 64: Rotating body (roller) / D1, D2: Conveyance direction / L1: Overall length section / N1: Image forming section (transfer nip) / N3: Abutting section (nip) / R4: Double-sided conveyance path / R5: Curved conveyance path / R5a: Upstream end / R5b: Downstream end / RT: Vertex / S: Sheet / S1: Leading end

Claims

1. A first conveying unit including a first roller that conveys a sheet and a second roller that rotates about the same rotation axis as the first roller and conveys the sheet; A second conveying unit that has a butting portion capable of forming a bend in the sheet when the leading end of the sheet conveyed by the first conveying unit abuts thereon, and conveys the sheet; A first guide that guides the sheet conveyed by the first conveying unit to the second conveying unit; A second guide that is opposed to the first guide and guides the sheet conveyed by the first conveying unit to the second conveying unit, and forms a conveying path including a curved curved region between the first conveying unit and the second conveying unit together with the first guide; A first rotating body that is disposed in the curved region and is configured not to nip the sheet conveyed by the first roller and the second roller; A second rotating body that is disposed in the curved region and is configured not to nip the sheet conveyed by the first roller and the second roller; A third rotating body that is disposed in the curved region and is configured not to nip the sheet conveyed by the first roller and the second roller, and includes: The conveying path and the first guide are disposed outside the curved region in the bending direction with respect to the second guide; The first rotating body, the second rotating body, and the third rotating body are disposed outside the curved region in the bending direction with respect to the second guide so as to be in contact with the surface of the sheet guided by the first guide and rotate passively; The first roller is disposed on one side with respect to the second roller in the width direction orthogonal to the sheet conveying direction; The first rotating body is disposed on the one side with respect to the first roller in the width direction; The second rotating body is disposed on the other side opposite to the one side with respect to the second roller in the width direction; The third rotating body is disposed between the first roller and the second roller in the width direction; The first rotating body, the second rotating body, and the third rotating body are disposed so as to overlap each other when viewed in the width direction; The first roller and the second roller correct the skew of the sheet by conveying the sheet in a state where the leading end of the sheet abuts on the butting portion; The first rotating body, the second rotating body, and the third rotating body rotate passively with respect to the sheet when the leading end of the sheet abuts on the butting portion and the skew of the sheet is corrected. A sheet conveying device characterized by the following.

2. The abutting portion is the nip portion of the registration roller pair, and by the leading end of the sheet conveyed by the first roller and the second roller abutting against the nip portion, it is possible to form a bend in the sheet. The sheet conveying device according to claim 1, characterized by the above.

3. The first roller and the second roller are configured to be able to sandwich and convey the sheet, and the conveying direction of the sheet by the first roller and the second roller and the conveying direction of the sheet by the registration roller pair are in substantially opposite directions. The sheet conveying device according to claim 2, characterized by the above.

4. The first roller and the second roller are configured to be able to sandwich and convey the sheet, and the angle formed by the conveying direction of the sheet by the first roller and the second roller and the conveying direction of the sheet by the registration roller pair is 120 degrees or more and 240 degrees or less. The sheet conveying device according to claim 2, characterized by the above.

5. The second conveying unit has an abutting portion capable of forming a bend in the sheet when the leading end of the sheet conveyed by the first roller and the second roller abuts, and a roller pair that sandwiches and conveys the sheet after the leading end of the sheet abuts against the abutting portion. The sheet conveying device according to claim 1, characterized by the above.

6. The first rotating body, the second rotating body, and the third rotating body are arranged so as to reduce the frictional resistance between the sheet in the curved region and the first guide. The sheet conveying device according to any one of claims 1 to 5, characterized by the above.

7. The first rotating body, the second rotating body, and the third rotating body are arranged along the conveying section from the upstream end of the conveying path to three-fifths of the entire length section from the upstream end to the downstream end of the conveying path in the sheet conveying direction. The sheet conveying device according to any one of claims 1 to 6, characterized by the above.

8. It further includes a fourth rotating body arranged in the curved region and configured not to nip the sheet conveyed by the first roller and the second roller. The fourth rotating body is arranged outside the curved region in the curved direction in the curved region rather than the second guide so as to be in contact with the surface of the sheet guided by the first guide and rotate passively. The first rotating body, the second rotating body, the third rotating body, and the fourth rotating body are arranged at different positions from each other in the width direction. The third rotating body and the fourth rotating body are arranged between the first roller and the second roller in the width direction. The sheet conveying device according to any one of claims 1 to 7, characterized in that.

9. The first rotating body and the second rotating body are arranged symmetrically with respect to the center of the conveying path in the width direction. The third rotating body and the fourth rotating body are arranged symmetrically with respect to the center of the conveying path in the width direction. The sheet conveying device according to claim 8, characterized in that.

10. The first rotating body, the second rotating body, and the third rotating body are rollers whose portions in contact with the surface of the sheet rotate in the sheet conveying direction. The sheet conveying device according to any one of claims 1 to 9, characterized in that.

11. The curved region is U-shaped, extends downward from the first roller and the second roller, and has a first region up to the apex of the U-shape, and is arranged downstream of the first region in the sheet conveying direction and extends upward to the second conveying portion. And a second region, The first rotating body is arranged in the first region. The second rotating body is arranged in the first region. The third rotating body is arranged in the first region. The sheet conveying device according to any one of claims 1 to 10, characterized in that.

12. A sheet conveying device according to any one of claims 1 to 11, And an image forming unit that forms an image on a sheet. An image forming apparatus, characterized in that.

13. It includes a duplex conveying path that guides a sheet on which an image is formed on a first surface back to the image forming unit again, The conveying path constitutes a part of the duplex conveying path. The image forming apparatus according to claim 12, characterized in that.

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